Numerical Simulation and Experiment for Defect Detection of Composites by Thermal Wave NDT

摘要

Since the use of advanced composite materials continues to increase in the area of aviation and navigation,the need for a quantitative,rapid,in-service inspection technology has become a critical concern throughout the industry and practice. Thermal Wave Nondestructive Testing (TW-NDT) technology,which has proved to be an effective method,was used to detect defects in composite materials of missile motor in this paper. Based on numerical analysis,the optimum parameters of heat flux and heating time for the best defect detectability was worked out theoretically. And also the factors influencing the testing sensitivity were further studied,including the defect size,depth,thickness and thermal diffusion coefficient,etc. The results show that TW NDT can identify the defect depth,size and position rapidly and effectively,and the bigger,nearer-surface and thicker of the defect,the easier to be inspected by this method. The most important factors which affect the sensitivity of TW inspection are the defect depth and heating parameters. Finally,experiment for a glass-fiber composites sample with three different diameters at different depths was investigated to verify the conclusions of numerical analysis. And image enhancement and segmentation methods were used to reduce noise and improve image contrast,which help to achieve defect recognition.